Feature Request: Expose sha256 in ls dependencies json

**Feature Request**

I would like the output of `stack ls dependencies json` to contain `sha256` and size of packages. AFAIK this information is already available in the snapshots, but currently not exposed through `stack`'s CLI.

**Motivation**

The upcoming release of `stack` contains the new [`stack ls dependencies json`](https://github.com/commercialhaskell/stack/pull/4424) feature which returns the package dependency graph and some additional package metadata for a given project (package names, versions, locations, dependencies) in a JSON format. This is very useful for build tools that would like to call out to `stack` to determine how to fetch sources of Stackage dependencies. The motivating use-case is Bazel with `rules_haskell`, see https://github.com/tweag/rules_haskell/issues/1310. Though this may also be beneficial for other build tools.